Jonathan Tweet

Native to Rock Island, Illinois, Tweet is the son of Roald Tweet, Augustana College professor emeritus and a popular local historian, and Margaret Tweet.

Jonathan Tweet started playing D&D in the 1970s, when his father gave him his first Dungeons & Dragons game. He briefly played with a group of college students, although he says, "but the DM killed me off... because he didn't want a twelve-year-old in his group". Tweet then formed his own gaming group by recruiting classmates. Tweet graduated from Rock Island High School class valedictorian in 1983. He majored in psychology and sociology at his parents' alma mater, St. Olaf College in Minnesota.

Jonathan Tweet and Mark Rein-Hagen founded Lion Rampant in 1987, while students at St. Olaf College where they also met Lisa Stevens who later joined the company. His article "Egyptian Magic for Call of Cthulhu" appeared in Different Worlds #47 (Fall 1987), the magazine's final issue. In 1987, Tweet and Rein-Hagen designed the game Ars Magica, a game centered around wizards in the Middle Ages. Tweet left Lion Rampant and the RPG industry in 1989 to start a new career. Tweet wrote Festival of the Damned (1991), an adventure published by Atlas Games for Ars Magica. Tweet continued to run a game for a group in Rock Island, Illinois, and wrote about the game "Al Amarja" in Alarums and Excursions; when John Nephew saw these A&E articles he wanted to publish the game, and the result was Over the Edge (1992), the first original game from Atlas Games. His design on Over the Edge notably involved free-form rules and a subjective approach. Lisa Stevens suggested that Tweet revise the Talislanta rules for Wizards of the Coast and write its first new adventure; this resulted in a revision of the Talislanta Guidebook (1992), which was soon followed by his adventure The Scent of the Beast (1992). Tweet wrote the adventure Apocalypse (1993) for Mayfair Games' Role Aids line. Nephew and Tweet also designed On the Edge (1994), a collectible card game based on Over the Edge. Tweet became a full-time employee of Wizards of the Coast in June 1994, and heralded in new lines from Wizards, the first of which was Ars Magica, recently acquired at Tweet's suggestion. Tweet designed Everway, which was first published by Wizards of the Coast in 1995. After Wizards of the Coast moved away from role-playing games, Tweet worked on Portal, a Magic: The Gathering set designed to help new players learn the game.

Tweet was lead designer on the third edition of Dungeons & Dragons. Tweet, Monte Cook, and Skip Williams all contributed to the 3rd edition Player's Handbook, Dungeon Master's Guide, and Monster Manual, and then each designer wrote one of the books based on those contributions. Tweet oversaw the team designing the Chainmail Miniatures Game, while Skaff Elias did the main design work and Chris Pramas designed the world. Tweet became the head of the miniatures group, and the Dungeons & Dragons Miniatures Game (2003) was primarily the work of Tweet, Rob Heinsoo, and Skaff Elias. On December 2, 2008 Tweet was laid off from Wizards of the Coast.

13th Age a d20 System RPG, designed by Heinsoo and Tweet was published by Pelgrane Press on August 3, 2013. The pre-release version was a nominee for the RPG Geek RPG of the Year 2013.

In 2015 Tweet published Grandmother Fish, a Kickstarter-funded book described as "the first book to teach evolution to preschoolers". While criticized by creationist organizations, it has been praised by science educators.

In 2018 Tweet, along with children's science illustrator Karen Lewis, released two card games, Clades and Clades Prehistoric. These animal matching games are intended to be used as tools to teach about evolution.

An atheist since grade school, Tweet has devoted much of his personal website to his views on religion, in particular on the historical Jesus. He also blogs about religion on the Secular Sunday School blog.

Tweet and his wife Tracy moved to Seattle, Washington in 1994. Tracy died from multiple sclerosis in 2008. He continues to live in the Seattle area with his daughter.